Composite Engine Cover with Foam Overmold for NVH Attenuation
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Solution Overview
Problem
The existing mounting systems for engine covers on internal combustion engines, which rely on multiple steel brackets and fasteners, lead to noise, vibration, and harshness issues, increased manufacturing costs, and complex installation due to a high parts count, while hard thermoplastic materials used for hinges are ineffective at attenuating noise and vibrations.
Innovation Solution
A composite engine cover with a rigid substrate overmolded with polyurethane foam, featuring a snap-in-place fastening system and integral hinge portions that eliminate the need for tool-based installation and additional fasteners, providing a combination of structural rigidity and noise absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steel brackets and fasteners are used to mount the engine cover, then the cover can be securely retained, but noise, vibration, and harshness problems increase
Solution Approach 1:
The engine cover uses a composite construction with a rigid substrate (metal or rigid plastic) providing structural strength and a foam body (polyurethane or other foam material) overmolded onto the substrate to provide noise and vibration attenuation. This composite structure maintains secure retention while reducing NVH problems compared to traditional steel bracket mounting.
2Reliability
If multiple brackets and fasteners are used for mounting, then secure retention is achieved, but parts count and manufacturing costs increase
Solution Approach 1:
The mounting system is integrated directly into the engine cover structure itself, eliminating the need for separate steel brackets and multiple fasteners. The hinge portion and socket portions are formed as integral parts of the composite engine cover, reducing the parts count while maintaining secure retention through the snap-in-place fastening system.
Solution Approach 2:
The composite structure of rigid substrate with overmolded foam body allows the mounting features to be directly formed in the cover itself, combining structural integrity with reduced parts count. The foam body can be molded with integrated mounting features that eliminate separate fastening components.
3Strength
If hard thermoplastic material is used for the entire cover, then rigid hinge attachment is achieved, but noise and vibration attenuation effectiveness decreases
Solution Approach 1:
The engine cover is constructed as a composite with a rigid substrate providing the necessary strength for hinge attachment, while a foam body (such as polyurethane foam) is overmolded onto the substrate. The foam material provides superior noise and vibration attenuation compared to solid hard plastic, while the rigid substrate ensures adequate hinge rigidity.
Solution Approach 2:
Different regions of the engine cover have different material properties optimized for their specific functions: the rigid substrate provides structural strength and rigidity where needed for hinge attachment, while the foam body provides noise and vibration attenuation in areas where these properties are most beneficial.
4Reliability
If traditional fasteners are used for securing the cover, then secure retention is achieved, but installation difficulty increases due to hard-to-reach locations
Solution Approach 1:
The mounting system is designed to be self-installing through a snap-in-place mechanism. The socket portions on the engine cover receive the structural projections on the intake manifold through a simple snapping action, eliminating the need for tools or complex fastening operations. The hinge portion provides automatic alignment and retention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves effective noise and vibration attenuation, simplifies installation, reduces parts count and manufacturing costs, while maintaining a competitive product with improved aesthetics and functionality.
Implementation Method 1
The foam body has first and second sockets releasably receiving the first and second projections, respectively, to hold the cover at an installed position. The composite engine cover obtains an attractive appearance and good noise absorption characteristics
Data Source
AI summary
A cover for an engine assembly of a motor vehicle is attached at one end by a hinge and at the other end by sockets interlocking with engine projections. The engine assembly has a first hinge portion located at a top, rearward end of the engine assembly, and has first and second structural projections extending upwardly and spaced from the first hinge portion. The cover has a foam body overmolded onto a rigid substrate. The substrate has an integral second hinge portion to engage the first hinge portion. The foam body is formed of polyurethane foam with first and second sockets releasably receiving the first and second projections, respectively, to hold the cover at an installed position. The soft cover provides excellent noise and vibration performance together with a desired visual appearance. Manual installation and removal of the cover is done easily and without any tools or removable fasteners.